Enclosure

ABSTRACT

The invention relates to an enclosure  12.  The enclosure  12  disclosed herein is arranged to house a heat generating component and comprises a top face, a rear face and a first side face. At least one of the first side face or the rear face comprises a substantially continuous portion and a venting portion  20.  The venting portion  20  has at least one vent opening to allow air to be vented from within the enclosure  12.  The venting portion  20  is recessed with respect to the substantially continuous portion of the respective face.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit and priority of Great Britain Application No. GB 1117481.0 filed Oct. 10, 2011, and Great Britain Application No. GB 1205781.6 filed Mar. 30, 2012. The entire disclosures of each of the above applications are incorporated herein by reference.

FIELD

The invention relates to an improved enclosure. In particular it relates to an improved enclosure for enclosing equipment or components which generate heat, for example a drive unit.

BACKGROUND

Many electronic components and electrical equipment are known to generate heat during operation. As a result, an enclosure which covers or houses such components or equipment must include suitable cooling means.

A drive unit (also simply referred to as a “drive”) is a well known piece of equipment, used in a wide range of mechanical systems. A drive unit includes and/or is connected to a motor which moves a load in a mechanical system. The drive unit also includes control means for controlling the speed of the motor. The drive unit includes electronic components, at least some of which generate heat during operation. This heat must be controlled in order to avoid over-heating, to ensure safe and efficient operation of the drive unit. The components which make up the drive unit are either completely housed within, or at least covered by, an enclosure.

It is common practice to arrange the components of a drive unit to include an extruded heat sink at the rear or bottom, with a PCB in front of or above the extruded heat sink. In such an arrangement, any heat-generating components within the drive unit that require cooling are placed in contact with the extruded heat sink and an enclosure (or “housing”) is positioned in front of or over the whole arrangement. The enclosure includes an opening through which the extruded heat sink can protrude, to channel heat away from the components inside the enclosure. Relatively large extruded heat sinks often make up some or all of the rear surface of a conventional drive unit.

Often, a drive unit will also include one or more openings or vents in its surface, to allow air flow through the inside of the enclosure, to assist with cooling. One or more fans can also be included within the drive unit, to circulate air. For example, it is common to include a fan towards the bottom of a drive unit and a vent in the top surface of the enclosure, so that the fan helps to push hot air upwards, out of the vent, and away from the components inside the enclosure.

In many practical situations, several drive units will need to be located close to each other. It is important that one drive unit does not cause heating of a nearby second drive unit. Therefore it can be undesirable for drive unit enclosures to include side vents, since these would cause adjacent drive units to direct hot air towards one another. This has made top surface venting a popular option for drive units.

In practice, drive units are usually mounted against a substantially planar vertical surface. For example they may be mounted against a wall or in a cabinet. This has also made top surface venting a popular option for drive units.

Known cooling solutions for drive units have several associated disadvantages. For example, using a linear heat sink for connection to any components within a drive unit that require cooling imposes a significant restriction on the possible selection and arrangement of components within the drive unit, which can limit the technical suitability of the drive unit for certain purposes. The use of such a heat sink also influences the physical size and shape of the drive unit, which can cause practical problems particularly if several drive units are to be used together at one location.

In addition; although, as mentioned above, top venting is a popular choice for drive units, it poses a contamination risk if a drive unit is to be used in an environment where dust, dirt or other particles will be in the air and thus could drop through the top vent, into the drive unit. Such contamination will potentially impair the operation of the drive unit, reducing its operational life, and can cause a significant safety risk. Also, this contamination risk also poses a restriction on the possible arrangements of components within the drive unit—for example it potentially precludes locating sensitive or expensive components at the top of the drive unit.

SUMMARY

An invention is set out in the claims.

According to an aspect, an enclosure is provided that is arranged to house a heat generating component. The enclosure comprises a top face, a rear face and a first side face, wherein either the rear face and/or the first side face comprises a substantially continuous portion and a venting portion, the venting portion having at least one vent opening to allow air to be vented from within the enclosure, wherein the venting portion is recessed with respect to the substantially continuous portion of the respective face.

The rear face of the enclosure may comprise a substantially continuous rear portion and a rear venting portion having at least one rear vent opening to allow air to be vented from within the enclosure, wherein the rear venting portion is recessed with respect to the substantially continuous rear portion. The rear venting portion may be provided on an upper part of a rear face of the enclosure. The rear venting portion may be provided on a sloping surface that connects part of the rear face to part of the top face of the enclosure. Additionally or alternatively, the rear venting portion may be provided on the surface of a cut-out, stepped-in or recessed part of the rear of the enclosure.

A side face of the enclosure may comprise a substantially continuous side portion and a side venting portion having at least one side vent opening to allow air to be vented from within the enclosure, wherein the side venting portion is recessed with respect to the substantially continuous side portion. The side venting portion may be provided on an upper part of a side face of the enclosure. Preferably, the top face of the enclosure is substantially continuous and has no openings therein.

The side venting portion and/or the rear venting portion may include one or more barriers partially covering respective vent openings, in order to prevent matter from entering the enclosure via the venting portions.

The enclosure may include a second side face comprising a second side venting portion. The second side face may be located substantially opposite the first side face. The enclosure may comprise a plurality of venting portions which can be distributed on one face or on a combination of two or more faces of the enclosure. A venting portion provided on a surface of the enclosure may be aligned with a cooling component, for example a heat sink, which is located within the enclosure.

The enclosure may comprise a drive unit.

The enclosure may house a barrier device, said barrier device being arrange to do at least one of: protecting a sensitive electronic component from an air flow; deflecting an air flow; providing an opening for location of a component therein; and thermally and/or electrically insulating an electronic component. For example, the barrier device may be arranged to locate a cooling component such as a heat sink. Additionally or alternatively, the barrier device may be arranged to deflect an air flow towards a component within the enclosure and/or towards a vent opening in a face of the enclosure.

According to an aspect a drive unit is provided wherein that drive unit comprises one or more heat generating components housed within an enclosure. The enclosure comprises at least one vent located on a side surface or a rear surface thereof. The enclosure does not comprise any vents on its top surface. Air or other gas within the enclosure that is heated by the heat generating component can be expelled from within the enclosure via the vent(s). Preferably the vent is located on a part of the enclosure that is narrower than the widest part of the enclosure. As a result, even if at its widest part the enclosure is closely confined or mounted against a surface, an air gap will still be provided for the heated air to escape from the vent(s).

According to an aspect a method of cooling components within a drive unit is provided. The method comprises housing the components within an enclosure wherein that enclosure has at least one vent on a side surface and/or on a rear surface thereof. Heated air in the vicinity of the component may be expelled through the vent, away from the interior of the drive unit. Preferably the vent is provided on a recessed portion of the surface of the enclosure, so that an air gap is provided to facilitate escape of the heated air away therefrom.

FIGURES

Embodiments will now be described by way of example in reference to the appended figures, of which:

FIG. 1 is a side perspective view of a drive unit;

FIG. 2 is another side perspective view of the drive unit of FIG. 1;

FIG. 3 is a rear view of a drive unit;

FIG. 4 shows a mechanical barrier device; and

FIG. 5 shows the mechanical barrier device of FIG. 4 used in conjunction with electronic components.

OVERVIEW

In overview, an improved enclosure is provided, said enclosure being arranged to include equipment or components which generate heat in operation. For example the enclosure may be for a drive unit.

The enclosure comprises a side vent and/or a rear vent. If there is more than one side vent, they may both be provided on the same side or they may be provided on different, for example opposite, sides of the enclosure. Preferably, the side vents are provided towards the rearmost part of the side(s) of the enclosure, away from a front face of the enclosure that can include a user interface for control input to and/or feedback from components housed within the enclosure.

If present, each side vent is provided on a recessed or “stepped in” part of the respective side of the enclosure. Therefore even if, at its widest part, the enclosure is located in a tight or confined space, there will still be a gap for air to escape from the side vent(s) in order to dissipate heat away from the inside of the enclosure.

If present, the rear vent is preferably provided towards the top of a rear surface of the enclosure, so that warm air vented therefrom escapes away from the vicinity of the enclosure and its enclosed components as quickly as possible. The rear vent is also preferably located within a recessed region, for example a part of the enclosure that is sloped away from or stepped in from the main surfaces of the enclosure, so as to provide space for air to escape from the rear vent even when the drive unit is located in a tight or confined space. Also, even if the drive unit is mounted against a surface, for example a substantially planar surface such as a wall or a face of a cabinet, the recessed region at the rear of the enclosure provides an air gap for air to escape from within the enclosure via the rear vent.

The enclosure preferably does not include any vents on its top surface. As a result, the risk of contamination entering the enclosure via its venting is substantially reduced as compared to prior art arrangements. This risk is further reduced by virtue of the design of the rear and/or side vents. For example they can include slats or other barriers over each venting opening, wherein those slats or other barriers cover the entrance to the respective opening and thus make it difficult for contamination to enter therein.

Inside the enclosure, the location of components, including heat generating components, can be chosen to work in conjunction with the rear and/or side venting in order to further optimise cooling inside the enclosure. For example, cooling components such as heat sinks can be aligned with the vents so that the heat which such heat sinks channel away from heat generating components within the enclosure can be dissipated readily via the vents. Unlike in conventional drive units, there is no need to have a single relatively large heat sink within the enclosure. Instead multiple smaller heat sinks at different respective locations may be used. In addition or alternatively, shielding can be used inside the enclosure in order to cover and therefore protect sensitive components from air flow within the enclosure. Such shielding may include one or more barriers for deflecting or channelling the air flow, for example it could be channelled from a heat generating component or a cooling component such as a heat sink towards a rear or side vent on the surface of the enclosure. An airflow could additionally or alternatively be chanelled by the shielding towards a component within the enclosure.

As a result, an effective venting system is provided which allows heat generating components within an enclosure to be kept cool and which reduces the risk of contamination entering the enclosure.

DETAILED DESCRIPTION

The improvements provided herein can be better understood with respect to the figures. In FIG. 1 a drive unit 10 comprises an enclosure or cover 12 which houses electronic components and other equipment (referred generally hereafter as “components”). A front face 14 of the cover 12 includes a control panel for user input to the drive unit 10. The cover 12 comprises a front housing 16, which includes the front face 14, and a rear housing 18 which is removably attachable to the front housing 16. The front housing 16 and rear housing 18 can attach to one another by any suitable inter-engagement means such as a snap fit or push fit.

The basic internal components which make up a drive unit (or “drive”) will be well known to the skilled person and so will not be discussed in detail herein. An AC motor drive consists of three basic stages in the transfer of electric power from the input to the output; 1) an Input Converter to convert AC input power to DC, 2) a DC link circuit consisting of capacitors and sometimes inductors to filter the DC voltage created by the Converter, and 3) an Inverter stage to convert the DC back to an AC output to power the motor. The Input Converter can use diodes, thyristors, or a mixture of both, or in some cases it uses transistors such as IGBT's or MOSFETS. The power devices used in the Converter can be included in a single package or be used in discrete form. The Inverter can use either IGBT's or MOSFETS which can also be in a single package or used in discrete form. In some forms, the Converter and Inverter can be encapsulated in the same package. All three stages of the power circuit can generate a significant amount of heat. As well as the power circuits, a drive typically also consists of control electronics to control a motor in the required way to turn the motor at the speed required by the user.

According to an embodiment, the components inside the drive unit 10 include a controller. The controller can be located anywhere within the drive unit 10, for example it can be located towards the top of the drive unit 10. Such a controller is important to the operation of the drive unit 10, therefore its operation must not be impaired by external factors such as contamination. It is also important for the controller and for other components within the drive unit 10 to be kept cool in order to optimise operational efficiency. With these considerations in mind, a conventional approach of using a fan towards the bottom of the drive unit to draw air up and through an exhaust vent on a top surface of the drive unit is not ideal.

The improvements described herein overcome the limitations of prior art cooling approaches and give rise to improved operational efficiency of components within a drive unit 10, such as the controller. This is achieved (at least in part) by careful shaping of the cover 12 of the drive unit 10, in particular of the rear housing 18 of the drive unit 10. The rear housing 18 shown in FIGS. 1 and 2 herein includes openings or vents at several locations on its surface.

For example, the drive unit 10 has a first side vent 20 located on an upper part of a first side 21 of its surface. It also has a rear vent 26 on a rear surface of the rear housing 18 (shown in FIG. 2) and may also have a second side vent on a second side surface. When two or more drive units 10 are to be located adjacent to one another, facing the same way as each other, it can be preferable for those drive units 10 to only have a vent on one side (for example the left hand side) so that adjacent drive units do not blow hot air into one another's side vents.

As mentioned in the background section above, conventional side venting can be disadvantageous if several drive units are to be used adjacent to one another, since one drive unit could vent hot air into a nearby drive unit. The drive unit 10 described herein overcomes this problem associated with conventional side venting through intelligent shaping of the cover 12. As can be seen in the figures, the rear housing 18 of the drive unit 10 is shaped so that an upper part of a first side 21 of the rear housing, which includes the first side vent 20, is recessed with respect to a lower part of the first side 21 of the rear housing 18, which is substantially continuous and does not include any vents, and also with respect to the corresponding first side of the front housing 16 to which the rear housing 18 attaches. As a result, the portion of the drive unit 10 which includes the first side vent 20 is narrower than the rest of the cover 12. When two such drive units 10 are placed side-by-side, the portion of one drive unit 10 which includes the side vent 20 will therefore be spaced apart from the nearest surface of the adjacent drive unit 10. This allows any hot air which escapes from the first side vent 20 to dissipate its heat in the air gap between the two drive units, therefore avoiding or at least reducing the risk of hot air from one drive unit 10 causing heating of the adjacent drive unit 10. The two drive units 10 can therefore be placed very close together, for example with the widest portions of their respective covers being flush side by side, which enables the drive units 10 to be arranged more compactly and thus to be located within a smaller area than is possible with prior art drive units. In addition, in practice the drive unit 10 may be mounted with its side(s) against a surface such as wall or the face of a cabinet. The recessed side venting provided herein enables air to escape from the first side vent 20 even if the drive unit 10 is to be mounted in such a manner.

As mentioned above, the drive unit 10 shown in FIGS. 1 and 2 also includes a rear vent 26. However, as can be best seen from FIG. 2, the drive unit 10 preferably does not include any conventional top surface venting. As can be seen in FIGS. 1 and 2, the top surface of the front housing 16 and the flat top surface 22 of the rear housing 18 do not include any openings or vents. At the rear of the flat top surface 22 of the rear housing 18, a downward sloping portion 24 is provided with a rear vent 26. The rear vent 26 has a slatted or louvre design wherein substantially horizontal vent openings are provided in the surface of the downward sloping portion 24 but there is a slat or louvre above each opening that is angled in such a way as to prevent ingress of falling dirt, dripping water or other contamination into the opening. Therefore rear venting is provided to allow exhaustion of hot air, in addition to the venting provided on the first side 21 of the drive unit 10, but that rear venting is provided in such a way as to minimise contamination risks.

The downward sloping portion 24 of the rear housing 18 slopes generally downwardly and rearwardly and adjoins to a flat, substantially vertical portion which makes up the remainder of the rear surface of the rear housing 18. Any number of louvres or slats can be provided, each protecting a respective opening, depending on the extent of heat generation and exhaust requirements for a particular drive unit 10. The specific rear venting arrangement shown in FIGS. 1 and 2 is only one possible example. Other arrangements are also possible, which provide space for rear venting even when a drive unit is to be fitted in a compact space and/or in close proximity with other similar drive units, or when it is to be mounted against a surface such as a wall or a face of a cabinet. One such arrangement is shown in FIG. 3. As can be seen therein, there is no sloping portion at the top of the rear of the drive unit 10 in FIG. 3. Instead, an upper portion of the rear face 30 includes a rear recess 32 which is “stepped in” from the rearmost, substantially planar part of the rear face 30. The rear recess 32 shown in FIG. 3 is substantially U-shaped in cross-section however it will be appreciated that other types of recess are possible.

A rear vent 34 is provided on one side of the rear recess 32. The rear vent 34 includes a plurality of rear vent openings. A barrier, slat or louvre is preferably provided over each rear vent opening, to protect it from contamination. Such barriers may be substantially horizontal, as shown in FIG. 3, or may be angled downwardly. The rear vent 34 can allow air to escape from the back of the drive unit 10. Because that rear vent 34 is provided within the rear recess 32, there is space for air from within the drive unit 10 to escape to at the rear of the product, even if the rear face 30 is situated up against a wall or other surface. Therefore heat can escape from the drive unit 10 from the rear as well as from one or more sides. As will be appreciated from the background section above, prior art drive units do not generally include rear venting but instead rely on top surface venting, which poses significant contamination risks to the components within a drive unit. This risk is reduced when rear venting as described herein is used instead of top surface venting.

The side venting in the improved enclosure is also designed to reduce contamination risks for the drive unit 10. As the skilled reader will appreciate, the risk of contaminants entering a drive unit via a side vent is generally lower than it would be for a top vent. To further reduce this risk, the side vent(s) in the drive unit 10 can be of a slatted or louvre design such as that described with respect to the rear venting above, wherein a slat or louvre is provided above each opening in the side vent, angled in such a way such as to prevent ingress of falling dirt, dripping water or other contamination into that opening. Even if a foreign body such as dirt, water or other particles did enter the drive unit 10 via the side vent(s), the sloping slats or louvres will ensure that any such contamination will fall past the venting and not block the venting. In addition, the location of components within the drive unit 10 can be selected so that the components will not be in the path of any falling contamination. For example, because the drive unit 10 does not need to include a single fixed-shape heat sink at the rear or bottom of the enclosure, such a heat sink will not be in the way if a foreign body does drop through the side vent 20 or rear vent of the drive unit 10.

By varying the surface venting on the enclosure of a drive unit as compared to prior art arrangements, the improvements described herein allow for, and can work in conjunction with, revision of the selection and location of components within the drive unit 10. For example, by providing more than one vent in a surface of the rear housing 18 of the drive unit 10, the improvements described herein increase the opportunities for that air to escape from the drive unit 10, and thus allow the components within the drive unit 10 to be kept cool. Furthermore, the use of multiple vents offers flexibility with respect to the selection and location of components inside the drive unit 10. For example it offers the option of using several heat sinks at different locations within a drive unit, rather than being restricted to one heat sink common to all heat generating components, as has been used in the past. Each of these heat sinks can preferably be smaller than the type of heat sink used in prior art drive units. This potential to use multiple smaller heat sinks provides a greater degree of freedom with respect to the selection and arrangement of components within the drive unit. For example, because all of the heat generating components are not restricted to being in a linear arrangement at one part of the drive unit, certain of the components in the drive unit can instead be relocated in order to better distribute the airflow within the drive unit. Furthermore, it removes the need to provide a large extruded heat sink at the rear of the drive unit, at least in some embodiments. The distribution of the airflow within the drive unit can be targeted so that cooling air from a fan and/or cooling air drawn in from a vent on the surface of the drive unit can be directed specifically towards heat generating components. Therefore assistance is provided to the heat sinks in cooling the inside of the drive unit.

Cooling with the drive unit can be further enhanced by the use of an apparatus inside the drive unit 10 for protecting electronic circuitry from potentially contaminated air. That apparatus may be provided in the form of a mechanical barrier device as described in more detail in co-pending GB patent application number 1117481.0, filed 10 Oct. 2011, in the name of Control Techniques Limited, the entire contents of which are incorporated herein by reference.

In addition to protecting sensitive electronic circuitry within a drive unit, the above-mentioned mechanical barrier device or other apparatus can manipulate air flow around the circuitry and/or can provide a mechanical connection between, or location of, cooling devices such as heat sinks and the electronic circuitry within a drive unit 10.

An example of a mechanical barrier device can be seen in FIG. 4 herein. The device 40 is moulded from a suitable material such as a heat resistant plastic. It may be formed from a fire-retardant Poly Carbonate or from a similar resin. It includes a base 42, a number of walls 44 extending upwards substantially perpendicular to the base 42, a plurality of openings 46 in the base 42 and a housing 48 also extending upwards substantially perpendicular to the base 42 and including a cut out portion 50.

The device 40 can be fitted around, over and/or in between electronic components which are to be protected. For example, as shown in FIG. 5 herein, the device 40 can be fitted over electronic components which are electrically connected to each other and/or to one or more PCB's 52. The device 40 shown in FIGS. 4 and 5 herein is designed for use in conjunction with two PCB's 52 which are connected together substantially at a right angle. A first plurality of electric components 54 is provided on the first PCB 52 a, wherein some of those components 54 have respective heat exchangers or heat sinks 58 connected to them. The heat sinks 58 extend substantially upwards from the horizontal PCB 52 a as shown in FIG. 5. A second electric component or plurality of components 56 is provided on the second PCB 52 b, again with one or more heat sinks 58 connected thereto, extending outwardly from the substantially vertical PCB 52 b.

In this case therefore, the openings 46 in the base of the device 40 enable a first plurality of components 54, and/or the heat sinks 58 to which they connect, to project substantially vertically upwards from the first PCB 52 a. Those components 54 and/or heat sinks 58 project through and above the base 42 of the device 40, without the device 40 causing any physical impediment to them. Similarly, the housing 48 which projects substantially vertically upwards from the base 42 of the device 40 can allow the second component(s) 56, or the heat sink(s) 58 connected thereto, to project outwards without causing any physical impediment or restriction. This is only one example—in practice, the physical configuration of the barrier device can be chosen so as to act as a mechanical shield which protects any selected electronic components, for example the sensitive areas on an electronic PCB assembly, to ensure that physical contaminants within air such as dust particles cannot settle on those areas. This reduces the chance of electrical failure of those due to physical (dust) contamination.

The mechanical barrier device 40 also provides protection of electronic circuitry against chemical contamination from cooling air. This is achieved by the physical configuration of the mechanical barrier device 40 being designed and manufactured so as to act as a blockade and thus prevent polluted air from blowing directly over sensitive electronic components. Thus, polluted air can be prevented from blowing directly over the surface of a PCB and sensitive components thereon, thereby minimising potential damage due to corrosion.

The mechanical barrier device 40 can include gaps or air holes at select locations, if the components at those locations are not particularly sensitive to contamination, to allow air to directly touch those locations. Alternatively or additionally, openings can be included to allow cooling devices such as heat sinks 58 to protrude therethrough, wherein those cooling devices can extend from electronic components that require cooling but are potentially sensitive to contamination. The cooling devices are air cooled, instead of the sensitive electronic component(s) being directly cooled themselves. As a result, air can still flow around or through areas of the electronic circuitry, or to cooling devices connected thereto, in order to cool the electric components during operation but at the same time not causing physical or chemical contamination to the circuit.

The mechanical barrier device 40 can include walls which provide electrical and/or thermal isolation between circuit components. It can also include holes or recesses which components can fit into or through. It can thus act as a locating means for those components, and can mechanically link them to other features such as a PCB.

A mechanical barrier device 40 such as the one shown in FIGS. 4 and 5 can work in conjunction with the recessed side and/or rear venting described herein. Multiple vents can be provided on a rear face and/or a side face, or a combination of the two, in order to align with cooling devices that are located by a mechanical barrier device 40. In addition or alternatively, the vents can be aligned with air flows that are determined by the ducting which such a device 40 provides. Because it has been recognised herein that recesses can be provided in the rear and/or in the side of the surface of an enclosure for a drive unit 10, enhanced flexibility is provided with respect to the possible arrangement of components inside a drive unit. This flexibility can be enhanced by the use of shields such as the mechanical barrier device 40, for protecting sensitive components whilst still encouraging air flow and cooling within a drive unit 10.

Hence a flexible, efficient, scalable and cost effective solution for cooling components within an enclosure such as a drive unit is provided.

Whilst particular embodiments have been shown and described herein, variations can be made thereon. For example, the improved enclosure may be implemented for other types of device, not just for a drive unit. Any suitable combination of rear venting and/or side venting may be used, depending on the heat generation and cooling requirements for the particular components and equipment making up a particular device. The enclosure may house any number or selection of electronic components or pieces of equipment. The enclosure and its venting features may be of any size or shape. Multiple such enclosures may be provided, for use separately or together.

Terms such as “front”, “back”, “rear”, “side”, “left”, “top”, “opposite”, “bottom”, “downwardly”, “vertical” and “horizontal” have been used herein with respect to the figures for illustrative purposes. These terms are not intended to be limiting. 

1. An enclosure, said enclosure being arranged to house a heat generating component and comprising a top face, a rear face and a first side face; wherein at least one of the first side face or the rear face comprises a substantially continuous portion and a venting portion; the venting portion having at least one vent opening to allow air to be vented from within the enclosure, wherein the venting portion is recessed with respect to the substantially continuous portion of the respective face.
 2. An enclosure as claimed in claim 1 wherein the rear face comprises a substantially continuous rear portion and a rear venting portion, the rear venting portion having at least one rear vent opening to allow air to be vented from within the enclosure, wherein the rear venting portion is recessed with respect to the substantially continuous rear portion.
 3. An enclosure as claimed in claim 1 wherein the first side face comprises a substantially continuous side portion and a side venting portion, the side venting portion having at least one side vent opening to allow air to be vented from within the enclosure, wherein the side venting portion is recessed with respect to the substantially continuous side portion.
 4. An enclosure as claimed in claim 2 wherein the rear venting portion is provided on a sloping surface that connects part of the rear face to part of the top face of the enclosure.
 5. An enclosure as claimed in claim 2 wherein the rear venting portion is provided on an upper part of the rear face of the enclosure.
 6. An enclosure as claimed in claim 3 wherein the side venting portion is provided on an upper part of the first side face of the enclosure.
 7. An enclosure as claimed in claim 1 wherein the top face is substantially continuous, with no openings therein.
 8. An enclosure as claimed in claim 2 wherein the rear venting portion comprises a barrier partially covering the rear vent opening, wherein the barrier is arranged to prevent matter entering the enclosure via the rear venting portion.
 9. An enclosure as claimed in claim 3 wherein the side venting portion comprises a barrier partially covering the side vent opening, wherein the barrier is arranged to prevent matter entering the enclosure via the side venting portion.
 10. An enclosure as claimed in claim 1 further comprising a second side face located substantially opposite the first side face, wherein the second side face comprises a second side venting portion.
 11. An enclosure as claimed in claim 1 wherein the enclosure comprises a rear face, a first side face, a second side face and a plurality of venting portions, said plurality of venting portions being provided on one of or a combination of: the first side face, the second side face or the rear face of the enclosure.
 12. An enclosure as comprised in claim 1 wherein the enclosure comprises a drive unit.
 13. An enclosure as claimed in claim 1 wherein the enclosure is arranged to house any of: a capacitor, an inductor, a diode, a thyristor, a transistor, an IGBT, a MOSFET or a heat sink.
 14. An enclosure as claimed in claim 1 wherein there is a cooling component provided within the enclosure and wherein the venting portion provided on a face of the enclosure is aligned with said cooling component.
 15. An enclosure as claimed in claim 14 wherein said cooling component comprises a heat sink.
 16. An enclosure as claimed in claim 1 wherein there is a barrier device provided within the enclosure, said barrier device being arrange to do at least one of: protecting a sensitive electronic component from an air flow; deflecting an air flow; providing an opening for location of a component therein; and insulating an electronic component.
 17. An enclosure as claimed in claim 16 wherein the barrier device is arranged to locate a cooling component such as a heat sink.
 18. An enclosure as claimed in claim 16 wherein the barrier device is arranged to deflect an air flow towards the vent opening in a face of the enclosure.
 19. An enclosure as claimed in claim 16 wherein a component is provided within the enclosure and wherein the barrier device is arranged to deflect an air flow towards said component. 